1. Field of the Invention
The present invention relates to an IC card loading detecting apparatus that can detect by simple means whether or not an IC card housing therein a CPU circuit is loaded on a terminal equipment.
2. Description of the Prior Art
Recently, pocket telephones have just started using IC cards housing therein a CPU (central processing unit) circuit. In this system, algorithms, memories of data and telephone numbers of telephone subscribers or the like are stored in the IC card. Inasmuch as the telephone subscriber uses the same IC card with any pocket telephones, then the IC card user has to pay for such telephone rate for each calling. In the portable telephone using the IC card, the IC card must be loaded onto the portable telephone reliably.
An example of a conventional IC card housing therein the above-mentioned CPU circuit will be described with reference to FIG. 1. As shown in FIG. 1 of the accompanying drawings, there is provided an IC card which is generally depicted by reference numeral 1. The IC card 1 houses therein a CPU formed of a ROM (read-only memory serving as a program memory), not shown and a RAM (random access memory serving as a data processing memory), not shown and an EEPROM (electrically erasable and programmable ROM serving as a data memory), not shown. The IC card 1 includes on its surface an input/output terminal unit 2 formed of a plurality of terminal groups in order to transmit and receive signals to and from an interface unit of terminal equipments, which will be described later on.
The above-mentioned input/output terminal unit 2 is placed on the IC card 1 at a predetermined position defined by the ISO (International Organization for Standardization) standards. The input/output terminal unit 2 is formed of two columns, each including four terminals. Respective terminals are depicted by reference numerals 2a to 2h and will be described in detail below. The terminal 2a is a VCC terminal (i.e., terminal to which an operation voltage of CPU housed in the IC card is supplied), the terminal 2b is an RST terminal (i.e., terminal to which a reset signal of CPU housed in the IC card is supplied), the terminal 2c is a CLK terminal (i.e., terminal to which an operation clock of CPU housed in the IC card is supplied), the terminal 2d is an RFU terminal (i.e., auxiliary terminal), the terminal 2e is a GND (ground) terminal, the terminal 2f is a VPP terminal (i.e., terminal to which a write voltage of memory IC is supplied), the terminal 2g is an I/O terminal (i.e., bidirectional data transmission terminal), and the terminal 2h is an RFU (i.e., auxiliary terminal). The IC card 1 includes a magnetic stripe 3 formed on its front surface and the IC card 1 is inserted into the terminal equipment along the direction shown by an arrow A.
A conventional method of detecting whether or not the IC card 1 is loaded on the terminal equipment will be described next with reference to FIG. 2.
As shown in FIG. 2, when the IC card 1 is inserted into a terminal equipment 4 through its insertion slot 4a, the IC card 1 presses a microswitch 5 at its contact member 5a provided in the terminal equipment 4 to turn on the microswitch 5, thereby making it possible to confirm that the IC card 1 is loaded on the terminal equipment 4 at its predetermined position. Under the condition that the IC card 1 is loaded on the terminal equipment 4, the respective terminals 2a through 2h of the input/output terminal unit 2 on the IC card 1 are electrically brought in contact with contacts 6a though 6h formed of spring members provided on an interface unit 6 of the terminal equipment 4 respectively as shown in FIG. 3 to thereby effect transmission and reception of signals between the CPU circuit of the IC card 1 and the terminal equipment 4.
When the loading of the IC card 1 on the terminal equipment 4 is detected by the above-mentioned arrangement, the microswitch 5 is used as a detection device so that assembly parts which are thicker than the IC card 1 are required in addition to the interface unit 6 that is needed to operate the IC card 1. If an apparatus itself which uses the IC card 1 as a part of its system application is large in size, then it is natural that a ratio between the IC card 1 and the interface unit 6 of the terminal equipment 4 occupies the whole area of the apparatus should be reduced. In portable equipments such as a pocket telephone or the like, products that are miniaturized to the pocket size must be taken into consideration. However, if a communication system itself becomes digitized, then a ratio that the circuits necessary for effecting the communication occupy the whole of the portable equipment is unavoidably increased. As a consequence, the mechanism portion such as the IC card and the interface unit is limited, in particular, in the thickness direction so that the portable equipment cannot be miniaturized substantially according to the above-mentioned conventional system.
Instead of the above mentioned microswitch, there is utilized a photo-interrupter device formed of a combination of a photo-diode and a light emitting diode as other detecting means. In this photo-interrupter device, the light emitting diode is energized by a current to emit a light and the photo-diode senses such emitted light. More specifically, during the photo-diode is energized, its forward resistance is low. If the photo-diode is disturbed in sensing a light, its forward resistance is changed and becomes high. Therefore, it becomes possible to detect the loading state of the IC card by effectively utilizing the above-mentioned features of the photo-interrupter.
On the other hand, there is proposed a detection method that does not need the above microswitch and photo-interrupter, i.e., detection method based on a software. A communication protocol between the IC card and a terminal equipment (host) utilizing the IC card is standardized by 7816-3 in the ISO standards. According to this detection method, the host apparatus determines regularly by utilizing a communication protocol whether or not the IC card is reliably loaded onto the interface portion of the host apparatus and whether or not an answer is normal. This method needs no parts separately but needs an operation electric power to regularly check whether or not the IC card is reliably loaded onto the interface portion and whether or not the answer is normal.
However, since the pocket-size portable telephone is small in size and limited in capacity of a battery that can be attached thereto, such pocket-size telephone takes every possible means for extending a communication time with a small electric power. Operation for checking whether or not the IC card is loaded onto the interface portion of the host apparatus must be frequently carried out during the communication in order to prevent the illegal use of the pocket telephone and the telephone line network. An electric power consumed by such checking fosters the reduction of the communication time.
For the above-mentioned reason, the conventional IC card loading detecting means cannot be applied to the small-sized portable telephone substantially.